The purpose of the proposed research is to define the nature of the hyper-responsive B-cell function in humans with systemic lupus erythematosus (SLE). Autonomous B-cell function, diminished suppressor T-cell function, or enhanced helper and/or amplifier T-cell function could all explain the abnormal B-cell immunity that occurs in SLE. Distinguishing these abnormalities in immunoregulation is possible by studying the antibody responses to a T-cell independent antigen. We will compare the quantity and immunoglobulin class of specific antibody produced in vivo and in vitro in response to a T-independent antigen in SLE patients to that of normals. We will also study the cellular regulation of in vitro T-independent and T-dependent B-cell responses in SLE patients. These studies will allow a detailed analysis of autonomous B-cell function and T-cell regulation of B-cell function in humans with SLE and may give insight into the pathogenesis of autoantibody formation in autoimmune diseases.